The Internet speed doesn't one into play here. It's the wireless speed. The Homehub 4 has N rated wifi at 5ghz so potentially that's up to 300mb/s. In real terms you'll never likely reach those speeds. But in any case USB 2 connected directly to your machine will likely be faster and more robust. They same would be true with a time capsule.

If you do want NAS functionality though you can either connected a USB disk to your Homehub or I'd suggest getting a dedicated NAS drive

Something else to consider is that FireWire devices can be daisy chained. Provided they have suitable connections on the enclosure.

External hard disk acquisition addict - but admitting the problem is the first step to a robust backupPlease use the reputation system if you think you've been helped - top right of this post